Voltage drop
 

I have new alternator battery is good all new wires to battery and alt but after it ruins for a few min the voltage drops to zero this is on a 2000 4.0 I have reset the computer by holding the cables together I'm at a end the only thing I have not replaced is the two wires that plug in to the alt.not sure how to check them any help would be great.

i would test all ground cables and recheck all your other cables. even clean up the ones to and from the starter.

Continuity check all wires with a DMM.

Sorry what is DMM

Oh boy.

Digital Multimeter.

I almost hit my screen when I saw your picture of the fly.

Sorry, as for the voltage drop, my 2000 does the same thing. it seems to be related to the alt getting wet or too low voltage itself. My alt puts out 14.6-14.8 volts even when the gauge says 0volts. I need time to get under my jeep and see if I have a corrosion problem or something.

Good luck and let us know what you find.+

I think your gauge is taking a dive! I just repalcaed my battery, It was dead, wouldn't hold a charge. But my alt gauge said 14.6 constantly. I checked with a meter, dead on. I would rather replace a battery, than a alt. JMO!

Just never called it that

I found out what my problem was a while back just now getting back to telling so if anybody else has the same problem it was blown fuse under the hood don't know why I never checked it but it was the fuse that goes to alt.

2000 jeep grand cherokee runs rough
 

need help with this one , my jeep 2000 grand cherokee 4.0 has very low
voltage barely moves up close to 0 . recently replaced pcm and cps .. because it would not start .. it first started when i lent it to my father in law and he connected battery backwards. the pcm had no asd or fuelpump working so i replaced it also scan showed cps was bad replaced it too... now it starts but it idles really bad so bad it jerks and sputters check gauge is on and abs light flickers on and off when idle... did key test for coded said done
the cps is aftermarket tomco brand not oem.. could the alternator be bad ?since from what i know jeeps are sensative to voltage... if its to low?:help:

Check the fuses. When Pops hooked the battery up wrong he may have blown a fuse, that would be a good thing. BUT, he may have fried the alternator or PCM, not good things. Maybe you should have treated his little girl better.

I don't know anything about Grand Cherokees but the XJ has a fusible link in the power cable that goes from the alternator to the bus bar on the end of the PDC (Green wire), which has been known to melt if the jumper cables were hooked up backwards.

To find out if the fusible link is open, disconnect the cable from the alternator and at the PDC bus bar and check for continuity in the cable using an Ohmmeter. If continuity is shown the link is good.